Epoxy resin composition for a fiber-reinforced composite material, yarn prepreg, and process and apparatus for preparing the same

ABSTRACT

To provide an epoxy resin composition suitable as a matrix resin for fiber reinforcement, and a yarn prepreg suitable in unwindability, excellent in higher processability due to drapability, high in the tensile strength of the epoxy resin composition after curing, and high in efficiency of the strength of reinforcing fibers. 
     A yarn prepreg, satisfying the following formulae (1) to (3): 
     
       
         50≦Wf≦80  (1)  
       
     
     
       
         20,000≦F≦100,000  (2)  
       
     
     
       
         F/8,000≦d≦F/2,400  (3)  
       
     
     where Wf is the content by weight of the fiber bundle (%), F is the number of filaments in the fiber bundle and d is the width of the prepreg (mm). 
     An epoxy resin composition for a fiber reinforced composite material, comprising at least the following components [A], [B] and [C]: 
     [A]: An epoxy resin mixture containing two or more epoxy resins, in such a manner that 100 weight parts of the epoxy resin mixture contains 40 to 79 parts of a monofunctional or bifunctional epoxy resin and 21 to 60 parts of a trifunctional or higher functional epoxy resin and that the epoxy resin mixture is 210 to 370 in epoxy equivalent weight 
     [B]: Fine particles containing a rubber ingredient and insoluble in the epoxy resins 
     [C]: A curing agent

TECHNICAL FIELD

The present invention relates to an epoxy resin composition suitable asa matrix resin for fiber reinforcement, and a yarn prepreg in whichreinforcing fibers are impregnated with an epoxy resin. Furthermore, thepresent invention relates to an intermediate material for a fiberreinforced composite material and a fiber reinforced composite materialobtained by using the yarn prepregs, and a concrete member reinforced bythe composite material. Moreover, the present invention relates to amethod for producing yarn prepregs, a method for winding a yarn prepreg,a method for producing a tube made of a fiber reinforced resin, and anapparatus for producing yarn prepregs.

A prepreg in which reinforcing fibers are impregnated with an epoxyresin composition can be processed into a desired form, for example, bylamination, winding, collection, etc., and the uncured epoxy resin canbe heated and cured by press molding, autoclave molding, etc. to obtaina composite material with a desired form such as a plate, tube or beam,etc.

Narrow prepregs called yarn prepregs, tow prepregs or strand prepregs(hereinafter called yarn prepregs) can be made into fiber reinforcedcomposite materials with various forms by methods described below.

Firstly, a yarn prepreg is wound around a core shaft at a predeterminedangle according to the tape winding method, then a heat shrinkable tapeis wound around it, and then it is heat-cured in an oven, to produce ahollow tubular composite material.

Secondly, yarn prepregs are laminated on a tool by the fiber placementmethod, covered with a bag film, placed into an autoclave, andheat-cured, to produce a composite material with a curved surface form.

Thirdly an intermediate material obtained by covering a plurality ofcollected yarn prepregs with fibers, preferably synthetic fibers can betwisted, and heated and cured, to produce a twisted cable of a compositematerial. Composite materials with such a form can be used as variouscables for bridges, braces of buildings, tension members of prestressedconcrete, reinforcing bars, rock bolts for ground reinforcement andcable bolts.

Furthermore, concrete members reinforced by twisted cables of a carbonfiber reinforced composite material can be used as marine structuresrequired to be corrosion resistant, concrete piles for a vertical shaftwhich can be directly excavated by a shield machine, etc.

BACKGROUND ART

Fiber reinforced composite materials with an epoxy resin as the matrixresin are widely used in general industrial fields such as aerospace,sports, civil engineering, architecture, etc., and hitherto prepregs,intermediate materials and composite materials obtained by combiningepoxy resins of various compositions and reinforcing fibers with variousproperties have been proposed.

A prepreg is generally like a sheet, and various reinforcing styles areavailable for respective purposes, for example, a prepreg withcontinuous fibers arranged in one direction in the flat face of thesheet, a prepreg provided as a woven fabric of continuous fibers, aprepreg with discontinuous fibers arranged in any desired direction,etc.

In addition to the above prepreg sheets, there are yarn prepregs inwhich carbon filaments arranged in one direction as a continuous fiberbundle are impregnated with a resin, and they are suitably used ascables for bridges, tension members of prestressed concrete, and membersfor fiber placement and filament winding. To prepare the yarn prepreg, acontinuous fiber bundle is impregnated with a resin and once woundaround a bobbin. Then, in the molding of a composite material, the yarnprepreg is unwound from the bobbin and provided for molding according tothe method as described before. So, the fiber arrangement, drapability,viscosity characteristic in resin curing, properties of cured resin,etc. greatly affect the properties, grade, etc. of the compositematerial.

Furthermore in recent years, as a result of pursuing the cost reductionof carbon fibers, carbon fibers of a thick fiber bundle with more than20,000 filaments have appeared, and a yarn prepreg using such carbonfibers has attracted attention. To impregnate the carbon fibers of athick fiber bundle homogeneously with a matrix resin, as a generalmethod, usually the fiber bundle is thinly widened by opening, etc., andhas the resin deposited on it to allow the resin to migrate easily inthe thickness direction of the fiber bundle. However, it is suggestedthat the yarn prepreg obtained by this method generates variousdisadvantages unless the width is appropriate. For example, if the widthis too large, torsion and folding-in in the transverse direction arelikely to occur at the guide portion in the step of arranging yarnprepregs in parallel in the production of a composite material, and as aresult, the composite material becomes low in the degree to whichtensile strength is translateed, etc. On the contrary, if the width istoo small (as a result, if the thickness is too large), the impregnationof the prepreg becomes insufficient, and the composite material obtainedgenerates defects such as voids, to lower the mechanical properties.

To translate excellent mechanical performance in general industrialfields such as aerospace, sports, civil engineering and architecture, itis important to let reinforcing fibers translate a high strength. Torealize this, the matrix resin used must be excellent in mechanicalproperties such as fracture toughness.

As prior art for yarn prepregs, JP-A-55-15870 proposes the use of amatrix resin with a thermoplastic resin added to a thermosetting resin,and JP-A-55-78022 proposes to add a high molecular epoxy resin of 5,000or more in molecular weight. However, both the methods have adisadvantage that if the yarn prepreg is allowed to stand for a longtime, the filaments stick to each other, to lose unwindability.Furthermore, it is proposed to mix a thermoplastic resin having amolecular weight of 10,000 or more, higher alcohol, higher fatty acid,etc. (JP-A-57-21428), and to mix a silicone resin and a silicone oil(JP-A-58-113226). These methods are effective to improve theunwindability and drapability of the yarn prepreg to some extent, butthe reinforcing fibers cannot translate a high strength.

In the examples of the above mentioned prior art, a carbon fiber bundleof 12,000 filaments only is referred to, and nothing is suggested as tothe method of improving the physical properties of a yarn prepreg usingcarbon fibers of a thick fiber bundle attracting attention in recentyears.

Japanese Patent Publication (Kokoku) No. 3-33485 concerning a method andapparatus for producing a yarn prepreg describes a method comprising thesteps of arranging in parallel reinforcing fibers like a sheet through aspacer on a sheet coated with a stage B thermosetting resin, laminatinga sheet on the other side, pressurizing and heating to impregnate thereinforcing fibers with a resin, slitting the sheet and the spacerportion by a slitter, and winding, or separating the resin impregnatedreinforcing fibers from the sheet, to obtain prepreg tapes. This methodis the most reliable method to allow the fibers to be impregnated with apredetermined amount of a resin accurately, but is disadvantageous inview of cost since a sheet is necessary for applying the resin and sinceraising the line speed is technically difficult.

Japanese Patent Publication (Kokoku) No. 5-80330 describes a method forproducing a yarn prepreg, comprising the steps of spreading a continuousfiber bundle, to make a band while carrying it; covering the band with aresin free from any solvent using a heating roller and a doctor blade;kneading the covered band, to impregnate the fibers with the resin;compressing the resin impregnated band; and finally cooling to providethe sectional form.

This method has a feature that the resin coating thickness on the fiberbundle in the covering step is controlled by the die interval or holebetween the roller and the doctor blade. So, this method is consideredto be more excellent than the method described in Japanese PatentPublication (Kokoku) No. 3-33485 having regard to productivity.

However, for the reason described below, it is considered difficult toprocess a plurality of continuous fiber bundles simultaneously.

First of all, when a case of using a flat roller without any groove onthe surface is considered, since the roller is coated on the surfacewith a uniform thickness of a resin in transverse direction, it iscoated with the resin also on the roller surface portions where thefiber bundle does not exist. The resin in these portions is likely to becarried away, being attached to both the edges in the width of the fiberbundle at the moment when the fiber bundle leaves the roller surface.So, at both the edges in the width of the fiber bundle, filaments arelikely to be broken and such problems as filament clinging occur.

Furthermore, when a case of processing a plurality of continuous fiberbundles at a time is considered, since fiber bundles arranged inparallel at a proper pitch are brought into contact with the rollersurface, the problem of filament breakage at both the ends of a fiberbundle occurs as many times as the number of continuous fiber bundles,and the method cannot be said to be excellent in productivity.

JP-A-8-73630 discloses a method of producing a tow prepreg, comprisingthe steps of supplying a predetermined amount of a resin to at least oneside of a flat tow using a discharge device, etc., to bring the resininto contact with the tow, for permeation into the thickness directionof the tow simultaneously or immediately after; homogeneouslyimpregnating the tow with the resin by the transverse movement of thefilaments constituting the tow; and cooling and winding. However, alsowith this method, it is considered to be difficult to process aplurality of continuous fiber bundles simultaneously for the same reasonas mentioned above.

Japanese Patent Publication (Kokoku) No. 5-80330 describes a step ofcovering the respectively opposite surfaces of bands. So, it can beeasily imagined that the problem of filament breakage increases for thesame reason as mentioned above.

Furthermore, Japanese Patent Publication (Kokoku) No. 5-80330 includesmany steps of kneading, compressing and cooling the resin impregnatedbands, and so many factors to raise equipment cost are involved.

Moreover, Japanese Patent Publication (Kokoku) No. 5-80330 describes amethod in which covering is executed on the surface of the rollernearest to a doctor blade. That is, at a position upstream of the doctorblade, the molten resin and the fiber bundle are brought into contactwith each other, and subsequently, the fiber bundle is passed throughthe clearance formed between the doctor blade and the roller surface, tocontrol the deposited amount of the resin.

In this method, since the resin is sucked into the clearance by the flowaccompanying the carried fiber bundle, a high impregnation effect can beexpected, but since the fluff of fibers is likely to clog on theupstream side of the blade, it is disadvantageously difficult to producea yarn prepreg continuously in a stable state.

Said Japanese Patent Publication (Kokoku) No. 3-33485 and JapanesePatent Laid-Open No. 8-73630 do not refer to the number of carbon fiberfilaments at all. Japanese Patent Publication (Kokoku) No. 5-80330refers only to a carbon fiber bundle with 12,000 filaments. None of themsuggests the method for improving the physical properties of a yarnprepreg using a thick carbon fiber bundle attracting attention in recentyears.

DISCLOSURE OF THE INVENTION

The object of the present invention is to provide a yarn prepreg using areinforcing fiber bundle large in the number of filaments, with asuitable width, good in unwindability and drapability to assure highprocessability, and high tensile strength and high efficiency ofreinforcing fiber strength after curing of epoxy resin, and also toprovide an intermediate material, a composite material and a concretemember reinforced by the composite material.

The present invention also provides a method and apparatus for producingyarn prepregs using a solvent-less resin excellent in process stabilityat high speed.

An embodiment of the yarn prepreg of the present invention is a yarnprepreg, comprising a reinforcing fiber bundle and an epoxy resin, andsatisfying the following formulae (1) to (3):

50≦Wf80  (1)

20,000≦F≦100,000  (2)

F/8,000≦d≦F/2,400  (3)

where Wf is the content by weight of the fiber bundle (%), F is thenumber of filaments in the fiber bundle and d is the width of theprepreg (mm).

An embodiment of the epoxy resin composition for a fiber reinforcedcomposite material of the present invention is an epoxy resincomposition for a fiber reinforced composite material, comprising atleast the following components [A], [B] and [C]:

[A]: An epoxy resin mixture containing two or, more epoxy resins, insuch a manner that 100 weight parts of the epoxy resin mixture contains40 to 79 parts of a monofunctional or bifunctional epoxy resin and 21 to60 parts of a trifunctional or higher functional epoxy resin and thatthe epoxy resin mixture is 210 to 370 in epoxy equivalent weight

[B]: Fine particles containing a rubber ingredient and insoluble in theepoxy resins

[C]: A curing agent

As a preferable embodiment of the yarn prepreg of the present invention,the above epoxy resin composition can be used.

An embodiment of the intermediate material for a fiber reinforcedcomposite material of the present invention is an intermediate materialfor a fiber reinforced composite material, comprising a plurality ofsaid yarn prepregs arranged with their fiber axes kept in parallel.

An embodiment of the fiber reinforced composite material of the presentinvention is a fiber reinforced composite material, comprising a curedsaid yarn prepreg or intermediate material.

An embodiment of the method for producing yarn prepregs of the presentinvention comprises the step of supplying a molten resin to the groovesof a rotating grooved roller, while bringing fiber bundles into contactwith the grooves of the grooved roller on the downstream side in therotating direction, to impregnate the fiber bundles with the moltenresin.

An embodiment of the method for winding a yarn prepreg of the presentinvention comprises the steps of impregnating a fiber bundle with aresin, and winding the yarn prepreg around a core coated with a materialexcellent in unwindability from the yarn prepreg, at an angle of 2 to40°.

An embodiment of the method for producing a tube made of a fiberreinforced resin of the present invention comprises the steps of windinga fiber bundle impregnated with a resin according to the above yarnprepreg production method, as it is, around a core according to thefilament winding method; heating it together with the core, for curingthe resin; and removing the core.

Another embodiment of the method for producing a tube made of a fiberreinforced resin of the present invention comprises the steps of windinga fiber bundle impregnated with a resin, as it is, around a core coveredwith a flexible tube according to the filament winding method; removingthe core only to leave a preform with the flexible tube; placing thepreform in a cavity of a mold; and heating with an internal pressureapplied to the flexible tube, for curing the resin.

An embodiment of the apparatus for producing yarn prepregs of thepresent invention comprises a grooved roller for impregnating a fiberbundle with a molten resin, and a molten resin supplying device forsupplying the molten resin into the grooves of the grooved roller.

The yarn prepreg of the present invention is excellent in higherprocessability and is highly capable of itranslatingthe tensile strengthof the composite material and the tensile strength of the reinforcingfibers after curing the epoxy resin.

The prepreg and intermediate material using the epoxy resin compositionof the present invention as a matrix resin is good in unwindability andhighly flexible, and the fiber reinforced composite material using theepoxy resin composition is excellent in tensile strength, that is, it ishighly capable of translating the tensile strength of the reinforcingfibers in the composite material. A concrete member reinforced by thefiber reinforced composite material has excellent mechanical properties.

The method and apparatus for producing yarn prepregs of the presentinvention allows yarn prepregs with a predetermined amount Wr of asolvent-less resin deposited to be produced efficiently and stably.

The Most Preferred Embodiments of the Invention

The present invention is described below in detail.

The number of filaments of a reinforcing fiber bundle used in the yarnprepreg of the present invention is in a range of 20,000 to 100,000. Ifthe number of filaments is smaller than 20,000, the productivity of thefiber bundle declines, and the homogeneity of the intermediate productdeclines. In the case of a fiber bundle with more than 100,000filaments, homogeneous impregnation cannot be achieved. The number offilaments is preferably in a range of 22,000 to 80,000, more preferablyin a range of 23,000 to 50,000.

The fiber content Wf by weight of the yarn prepreg of the presentinvention is in a range of 50 to 80%, and if the number of filaments isF, the width (d) is in the range shown by the following formula (3):

F/8,000≦d≦F/2,400  (3)

If the width (d) is smaller than the value of the left hand side of theabove formula (3), the thickness of the prepreg is too large, and forexample, when the prepreg is wound around a core for molding a compositematerial, the molded product is likely to have level differences on thesurface. Furthermore, in the prepreg, voids are likely to be formed, tolower the degree to which the tensile strength of the fibres istranslateed. On the contrary, if the width (d) is larger than the valueof the right hand side, the prepreg is too wide, and torsion and thefolding-in in the transverse direction are likely to occur at the guideportion in the step of arranging yarn prepregs in parallel for producinga composite material, being disadvantageously likely to generate fluff.As a result, the degree to which the tensile strength of the reinforcingfibers of the composite material is impregnated declines. The width (d)is preferably F/7,000≦d≦F/2,700, more preferably F/6,000≦d≦F/3,000.

The thickness of a yarn prepreg cannot be accurately measured by amethod of maintaining a micrometer, etc. in direct contact with theprepreg, since the prepreg is deformed. Therefore, the thickness (mm) ofa prepreg is calculated from the following formula, using the densityρ_(CF) of the fibers, the density ρ_(RESIN) of the cured resin, thecontent by weight Wf (%) of the fibers, the width d (mm) of the prepreg,and the weight P (g) per 1 m length of the prepreg:${{Thickness}\quad {of}\quad {prepreg}} = {\frac{P_{cf}}{d} \times \left\lbrack {\frac{1}{P_{CF}} + \frac{\frac{100}{Wf} - 1}{P_{RESIN}}} \right\rbrack}$

In this case, the unit weight (P_(cf)) of the fibers, the density(ρ_(CF)) of the fibers, and the density (ρ_(RESIN)) of the cured resinare measured according to the following methods:

Unit weight (P_(cf)) of fibers

A load is applied to the fiber strand to keep it straight under tensionwithout causing elongation strain, and a 1 mm long specimen is cut off.It is formed like a ring of about 5 cm, and its weight is measured asP_(cf).

Density (ρ_(CF)) of fibers

The same specimen as the above annular specimen is prepared, and itsmass (m₁) in air is measured. Then, the annular specimen is immersed inortho-dichlorobenzene, to sufficiently degas the specimen. Then, in theliquid, the mass (m₂) is measured. The density is calculated from thefollowing formula:

ρ_(CF) ={m ₁/(m ₁ −m ₂)}xp′(density of immersion liquid)

Density (ρ_(RESIN)) of cured resin

The mass (m₁) of a cured resin specimen in air is measured. Then, thespecimen is immersed in methanol to sufficiently degas the specimen, andin the liquid, the mass (m₂) is measured. The density is calculated asdescribed for the above density of fibers.

If the content by weight Wf of fibers is smaller than 50%, theavailability of the tensile strength of the fibers to the compositematerial is low. On the contrary if Wf is larger than 80%, the voids inthe composite material, stress concentration, etc. lower the tensilestrength. Wf is preferably in a range of 60% to 78%, more preferably ina range of 65% to 76%.

In the present invention, if continuous carbon fibers which aresubstantially untwisted are used, the strength of the carbon fibers ishighly translateed in the composite material, and such fibers areespecially suitable for applications requiring a high tensile strength,such as a twisted cable of a fiber reinforced composite material, etc.In this case, having regard to cost and processability, the weight ispreferably 1.3 to 8.0 g/m.

If the carbon fibers are twisted, the prepreg produced by using them andthe composite material produced by using the prepreg may decline instrength, since the filaments constituting the fiber bundle are notarranged in parallel.

As continuous carbon fibers which are substantially untwisted,quantitatively, carbon fibers of 10 cm or more, more preferably 12 cm ormore in hook drop value are preferable. The hook drop value is obtainedby vertically suspending a carbon fiber bundle in an atmosphere of 23°C. and 60% humidity, hooking a weight of 12 g on to it, and measuringthe descending distance of the weight 30 minutes later. This value issmall if the fiber bundle is twisted.

Carbon fibers having a tensile elastic modulus of 200 GPa or more andfracture strain energy of 38,000 kJ/m³ or more can also translate theirstrength to a sufficient extent in a composite material, and areespecially suitable for applications requiring a high tensile strength.The tensile elastic modulus is a value E measured according to JIS R7601, and the fracture strain energy refers to W calculated from formulaW=σ²/2E using the tensile strength and the above E value measuredaccording to JIS R 7601.

If a prepreg and a fiber reinforced composite material are produced byusing carbon fibers smaller than 200 GPa in tensile elastic modulus, thesectional area must be larger to keep the deformation of the compositematerial within the design tolerance. So the effect of weight reductionis small, and the product may be able to be used only for limitedapplications. For example, when the fiber reinforced composite materialof the present invention is applied as a cable for a bridge or a tensionmember of prestressed concrete, it becomes difficult to keep thedisplacement under tensile stress within a predetermined range.

If the fracture strain energy of carbon fibers is less than 38,000kJ/m³, it is difficult to translate the strength of carbon fibers to asufficient extent in a composite material, especially as a tensionmember such as a cable for a bridge or a tension member of prestressedconcrete.

The diameter of the carbon fibers used in the present invention ispreferably 3 to 10μ. If the diameter of carbon fibers is too thin, fluffis likely to be generated, and the fiber handling convenience and resinimpregnability in the step of epoxy resin impregnation become low. Onthe other hand, if they are too thick, the fiber bundle becomes toostiff, and, unpreferably the fibers cannot smoothly pass at guideportions, etc. in the step of epoxy resin impregnation.

The epoxy resin used for the yarn prepreg of the present invention isnot especially limited as far as it is used for fiber reinforcedcomposite materials, and translate to a sufficient extent the strengthof the carbon fibers when a composite material is produced from theprepreg, the tensile elongation of the cured epoxy resin is preferably5% or more.

The tensile elongation of a cured resin is obtained by the followingtension test. The tension test is executed by adhesion of a strain gaugeto a specimen made by a machine forming a dumbbell specimen according tothe method stated in JIS K 7113 from a 2 mm thick resin sheet, andpulling it at a tensile speed of 1 mm/min. The resin curing conditionsare 130° C. for 2 hours when dicyandiamide is used as a curing agent incombination with a curing auxiliary, and 180° C. for 2 hours whendiaminodiphenyl-sulfone is used as a curing agent.

The yarn prepreg of the present invention preferably has a moderateresin/fiber adhesive strength. The adhesive strength can be achieved bykeeping the interlaminar shear strength in a range of 65 to 140 MPaamong the properties of the composite material obtained by curing aprepreg. The interlaminar shear strength is more preferably in a rangeof 75 to 120 MPa. If the interlaminar shear strength is smaller than 50MPa, its durability in use as a tensile structural member declines. Onthe other hand, if larger than 140 MPa, the availability of tensilestrength declines. This interlaminar shear strength range can beachieved by adjusting the surface treatment of carbon fibers, theelastic modulus of the resin and the interfacial bonding strength.

The epoxy resin used in the yarn prepreg of the present invention can beused in combination with one or more additives generally used formodifying epoxy resins such as thermoplastic resins, elastomers andinorganic particles.

The epoxy resin composition for a fiber reinforced composite material ofthe present invention contains at least components [A], [B] and [C].

The unwindability and flexibility of the prepreg are greatly affected bythe composition of the epoxy resins as the component [A]. Theimprovement in the tensile strength of the composite material dueconsiderably to the addition of the component [B], but is also affectedby the composition of the component [A] used in combination.

As the component [A], 100 weight parts of an epoxy resin mixturecontaining two or more epoxy resins contain 40 to 79 parts of amonofunctional or bifunctional epoxy resin and 21 to 60 parts of atrifunctional or higher functional epoxy resin, and the epoxy resinmixture is 210 to 370 in epoxy equivalent weight, to keep both thecontradictory properties of unwindability and flexibility good. If theepoxy equivalent weight exceeds 370, flexibility cannot be obtained, andif the epoxy equivalent weight is less than 210, adhesiveness is sostrong as to lower unwindability. The epoxy equivalent weight ispreferably 220 to 360, more preferably 230 to 350. In view of thetensile strength of the composite material as a cured product, a veryhigh crosslinking density is not preferred. That is, if the amount ofthe trifunctional or higher functional epoxy resin is too large, tensilestrength declines. However, to keep good heat resistance, thetrifunctional or higher functional epoxy resin must be present in anamount in said range. The amount of the monofunctional or bifunctionalepoxy resin is preferably 45 to 75 parts, more preferably 50 to 70parts. Furthermore, the trifunctional or higher functional epoxy resin,preferably a trifunctional or tetrafunctional epoxy resin is preferablypresent in an amount of 23 to 55 parts, more preferably 25 to 50 parts.

To obtain a composite material high in tensile strength after curingwith the flexibility of the prepreg maintained, it is preferable toinclude a bifunctional epoxy resin of 50 poises or less in viscosity at25° C. Especially when a bifunctional epoxy resin of 10 poises to 0.1poise in the viscosity at 25° C. is present in an amount of 5 to 20weight parts in 100 weight parts of all the epoxy resins, theflexibility of the prepreg and the unwindability of the yarn areexcellent. Furthermore, if, as is preferred, an epoxy resin of 5% ormore in the tensile elongation when cured by heating at 130° C. for 2hours is used as a matrix resin, the composite material obtained isexcellent in tensile strength. Similarly, if, as is preferred, an epoxyresin of 1.3MN/m^(3/2) in fracture toughness K_(1c) when cured byheating at 130° C. for 2 hours is used as a matrix resin, the compositematerial is excellent in tensile strength. The use of an epoxy resin of1.5 MN/m^(3/2) or more in K_(1c) is more preferable. The tensile test ofa cured resin in this case is performed by adhesion of a strain gauge toa specimen made by a machine forming a dumbbell specimen according tothe method stated in JIS K 7113 from a 2 mm resin sheet, and pulling ata tensile speed of 1 mm/min. The fracture toughness test of a curedresin is performed using a 6 mm thick resin sheet by one-side notchedthree-point bending according to ASTM D 5045-91.

The bifunctional epoxy resin used as an ingredient of the component [A]can be selected, for example, from bisphenol A type epoxy resins,bisphenol F type epoxy resins, biphenyl type epoxy resins, naphthalenetype epoxy resins, dicyclopentadiene type epoxy resins, diphenylfluorenetype epoxy resins and their combinations.

As such bisphenol type epoxy resins, for example, marketed bisphenol Atype epoxy resins include Epikote 827 (180 to 190 in epoxy equivalentweight), Epikote 828 (184 to 194 in epoxy equivalent weight), Epikote1001 (450 to 500 in epoxy equivalent weight), Epikote 1004 (875 to 975in epoxy equivalent weight) (these are produced by Yuka Shell EpoxyK.K.), YD 128 (184 to 194 in epoxy equivalent weight) (produced by TotoKasei K.K.), Epiclon 850 (184 to 194 in epoxy equivalent weight),Epiclon 855 (183 to 193 in epoxy equivalent weight), Epiclon 860 (230 to270 in epoxy equivalent weight), Epiclon 1050 (450 to 500 in epoxyequivalent weight) (these are produced by Dainippon Ink & Chemicals,Inc.), ELA128 (184 to 194 in epoxy equivalent weight) (produced bySumitomo Chemical Co., Ltd.), DER331 (184 to 194 in epoxy equivalentweight) (Dow Chemical), etc. Bisphenol F type epoxy resins includeEpiclon 830 (165 to 185 in epoxy equivalent weight) (Dainippon Ink &Chemicals, Inc.) and Epikote 807 (160 to 175 in epoxy equivalent weight)(produced by Yuka Shell Epoxy K.K.). Biphenyl type epoxy resins includeYX4000 (180 to 192 in epoxy equivalent weight) (produced by Yuka ShellEpoxy K.K.). Naphthalene type epoxy resins include HP-4032 (140 to 150in epoxy equivalent weight) (produced by Dainippon Ink & Chemicals,Inc.). Dicyclopentadiene type epoxy resins include EXA-7200 (160 to 285in epoxy equivalent weight) (produced by Dainippon Ink & Chemicals,Inc.). Diphenyfluorene type epoxy resins include EPON HPT1079 (250 to260 in epoxy equivalent weight) (produced by Shell), etc.

The trifunctional or higher functional epoxy resin used as an ingredientof the component [A] can be selected, for example, from phenol novolaktype epoxy resins, cresol novolak type epoxy resins, glycidylamine typeepoxy resins such as tetraglycidyl diaminodiphenylmethane, triglycidylaminophenol and tetraglycidylamine, glycidyl ether type epoxy resinssuch as tetrakis(glycidyloxyphenyl)ethane and tris(glycidyloxy)methane,and their combinations.

Trade names of marketed phenol novolak type epoxy resins include Epikote152 (172 to 179 in epoxy equivalent weight), Epikote 154 (176 to 181 inepoxy equivalent weight) (these are produced by Yuka Shell Epoxy K.K.),DER438 (176 to 181 in epoxy equivalent weight) (produced by DowChemical), EPN1138 (176 to 181 in epoxy equivalent weight), 1139 (172 to179 in epoxy equivalent weight) (these are produced by Ciba Geigy), etc.

Cyclohexanedimethanol diglycidyl ether or resorcinol diglycidyl ether isa bifunctional epoxy resin of less than 10 poises in the viscosity at25° C., and if a mixture consisting of 100 weight parts of either ofthem, 4 weight parts of dicyandiamide and 4 parts ofdichlorophenyldimethylurea is cured by heating at 130° C. for 2 hours, apreferred epoxy resin of 5% or more in the tensile elongation as a curedresin can be prepared. It is especially preferable to include 5 to 20weight parts of either or both of the epoxy resins in 100 weight partsof all the epoxy resins of the component [A].

To improve the toughness of a matrix resin, it is known to add rubberparticles. For example, Japanese Patent Laid-Open (Kokai) Nos. 58-83014and 59-138254 disclose a method in which monomers containing functionalgroups capable of reacting with an epoxy resin such as an acrylate andacrylic acid are polymerized in an epoxy resin to disperse rubberparticles in the epoxy resin.

If a resin composition in which fine particles substantially insolublein epoxy resins at lower than 80° C. and containing a rubber ingredientas the component [B] are mixed with epoxy resins is molded and cured,the cured product shows a glass transition temperature (Tg) equivalentto the Tg of a resin composition not containing fine particles since thefine particles are insoluble in the epoxy resins. Furthermore, ascompared with a case of adding a liquid rubber, since the morphologyremains the same irrespective the difference in epoxy matrix or curingconditions, a stable cured product can be obtained characteristically.

It has been known that the component [B] is generally effective forimproving the toughness of a resin. However, the inventors found that ifa resin with the component [B] added to the component [A] is combinedwith reinforcing fibers, the tensile strength of the composite materialis remarkably improved unexpectedly. Thus, the present invention hasbeen completed. This can never be thought of from a finding that thephysical properties of the conventional fiber reinforced compositematerials in the fiber direction are dominated by the properties of thereinforcing fibers.

The fine particles containing a rubber ingredient and insoluble in anyepoxy resin can be, for example, crosslinked rubber particles consistingof a rubber phase only or a core/shell polymer consisting of a rubberphase and a non-rubber resin phase, etc.

The crosslinked rubber particles can be particles of a crosslinkedrubbery random copolymer obtained by copolymerizing an unsaturatedcompound or an unsaturated compound with a functional group and acrosslinkable monomer, etc.

The unsaturated compound can be, for example, a conjugated dienecompound such as butadiene, dimethylbutadiene, isoprene, chloroprene orany of their derivatives, a (meth)acrylate such as methyl(meth)acrylate, propyl (meth)acrylate or butyl (meth)acrylate, any ofunsaturated hydrocarbon compounds such as olefins and aromatic vinylcompounds.

The functional group of the unsaturated compound can be, for example, acarboxyl group, epoxy group, hydroxyl group or amino group, etc. Becauseof moderate reaction with a resin composition consisting of an epoxyresin and a curing agent, a carboxyl group, acid anhydride group orepoxy group is preferable.

The crosslinkable monomer can be a compound with a plurality ofpolymerizable double bonds in the molecule such as divinylbenzene,diallyl phthalate or ethylene glycol dimethacrylate.

For polymerization, various conventional polymerization methods such asemulsion polymerization, suspension polymerization and solutionpolymerization can be used. For emulsion polymerization, anyconventionally known method can be used. For example, monomerscontaining several unsaturated compounds and, as required, acrosslinkable monomer are emulsion-polymerized at a certain temperature,using a radical polymerization initiator such as a peroxide catalyst, anemulsifier such as an anionic, cationic, nonionic and/or amphotericsurfactant, in the presence of a molecular weight regulator such asmercaptan or halogenated hydrocarbon, and after a predeterminedpolymerization conversion has been reached, a reaction terminator isadded to terminate the polymerization reaction. Then, the unreactivemonomers in the polymerization system are removed by steam distillation,etc., to obtain a copolymer latex. A marketed product can also be used.Marketed crosslinked rubber particles include, for example, XER-91(produced by Japan Synthetic Rubber Co., Ltd.), CX-MN series (producedby Nippon Shokubai), YR-500 series (produced by Toto Kasei), etc.

A core/shell polymer is spherical fine particles usually consisting of acore phase and a shell phase, and a polymer with a double structureconsisting of a core and a shell, a core/shell polymer with a multiplestructure consisting of a soft core, hard shell and soft shell, etc. areknown. Among them, a core/shell polymer with a structure in which a softcore made of an elastomer material is covered with a hard shell obtainedby polymerization, and a core/shell polymer with a three-layer structurein which an elastomer shell covering a hard core is polymerized andfurthermore covered with a hard shell as the outermost layer can besuitably used since they are easily dispersed into the epoxy resin, ascompared with core/shell polymers with other structures.

The material of the core can be selected, for example, frompolybutadiene, polyacrylates, polymethacrylates, polybutyl acrylate,styrene-butadiene polymer, ethylene polymer, etc. The material of theshell can be selected, for example, from polystyrene, polyacrylonitrile,polyacrylates, polymethacrylates, polymethyl methacrylate, etc.

In the case of a core/shell polymer, it is preferable that the corecontent is 10 to 90 wt %, while the shell content is 90 to 10 wt %. Ifthe core content is less than 10 wt %, a sufficiently high strengtheffect cannot be obtained. If more than 90 wt %, it can happen that thecore cannot be perfectly covered with the shell, that when it is mixedwith an epoxy resin, the viscosity of the resin increases with the lapseof time, and that the physical properties of the composite material aredispersed. A preferable core content range is 60 to 90%.

The core/shell polymer can be produced by any of the methods disclosedin U.S. Pat. No. 4,419,496, European Patent No. 45,357 and JapaneseLaid-Open (Kokai) No. 55-94917. Marketed products can also be used.Marketed core/shell polymers include, for example, Paraloid EXL2655(produced by Kureha Chemical Industry Co., Ltd.), TR2122 (produced byTakeda Chemical Industries, Ltd.), EXL-2611, EXL-3387 (produced by Rohm& Haas), etc.

A plurality of kinds of fine particle containing a rubber ingredient andinsoluble in any epoxy resin described above can also be used incombination.

The particle size of the fine particles is preferably 10 μm or less,more preferably 5 μm or less, still more preferably 1 μm or less. If theparticle size is larger than 10 μm, it can happen that when thereinforcing fibers are impregnated with the matrix resin, the fineparticles are not homogeneously dispersed, to form a heterogeneousmolded product. Especially when, as is preferred the particle size is 1μm or less, the fiber orientation is not disturbed even in the case of acomposite material as high as 50 vol % or more in reinforcing fibercontent, and the effect of improving the tensile strength is remarkable.On the other hand, if the fine particles are too small, the effect ofimproving the tensile strength is lost. So, the particle size ispreferably 0.01 μm or more, more preferably 0.05 μm or more.

The proper amount of the component [A] is 1 to 20 weight parts against100 parts by weight of the epoxy resins. If the amount is less than 1part by weight, the effect of improving the tensile strength is small,and if more than 20 parts by weight, the viscosity of the resincomposition is so high as to make the impregnation into the reinforcingfibers difficult.

The component [B] is effective for improving toughness, especially thefracture toughness in a peeling-off mode.

The curing agent used as the component [C] can be selected from aromaticamines such as diaminodiphenylmethane and diaminodiphenylsulfone,aliphatic amines, imidazole derivatives, dicyandiamide,tetramethylguanidine, thiourea added amines, carboxylic anhydrides suchas methylhexahydrophthalic anhydride, carboxylic acid hydrazides,carboxylic acid amides, polyphenol compounds, novolak resins,polymercaptan, Lewis acid complexes such as boron trifluoride ethylaminecomplex, etc.

These curing agents which are microencapsulated can also be suitablyused for improving the storage stability of the prepreg.

Any of these curing agents can be used in combination with a suitablecuring accelerator to improve the curing activity. Preferablecombinations include S dicyandiamide and a curing accelerator, forexample, a urea derivative such as3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) or an imidazolederivative, and a carboxylic anhydride or novolak resin and a curingagent such as a tertiary amine.

where R₁ and R₂ stand for, respectively independently, any group such asH, Cl, CH₃, OCH₃ or NO₂ (n=1 or 2).

A preliminary reaction product of all or some epoxy resins and a curingagent can also be added to the composition. This method may be effectivefor viscosity control and storage stability improvement.

For controlling the viscosity of the resins and the handling convenienceof the prepreg, a thermoplastic resin can also be added to the epoxyresin composition for a fiber reinforced composite material containingthe components [A], [B] and [C]. Because they are compatible with theepoxy resins and have no adverse effect on the physical properties ofthe composite material, preferable thermoplastic resins includepolyvinyl formal, polyvinyl butyral, polyethylene oxide, polymethylmethacrylate, polyamides, polyesters, polyether sulfones, polysulfones,polyether imides, polyimides, etc. Two or more of these resins can alsobe used as a mixture.

The epoxy resin composition containing the components [A], [B] and [C]can be preferably used for the above mentioned yarn prepreg, and canalso be used for other applications such as electronic materials andadhesives other than the fiber reinforced composite materials.

The present invention also provides an intermediate material in which aplurality of said yarn prepregs are arranged with their fiber axes keptin parallel like a sheet or bundle, without being twisted.

An intermediate material sheet is obtained by arranging yarn prepregslike a sheet by the conventionally known drum winding method.

The intermediate material bundle referred to here can be, for example, amaterial in which the yarn prepregs are fixed in the collected positionin the cross section and in which the reinforcing fibers in all the yarnprepregs are arranged in parallel in an axial direction or a material inwhich these yarn prepregs are braided with polyester fibers, etc., as isknown in the prior art (for example, as described in JP-A-6-93579). Forcovering, as described in JP-A-6-93579, fibers or a narrow syntheticfilm can be wound around the arranged yarn prepregs. The coveringmaterials which can be used are fibers and synthetic films of variousmaterials such as polyesters, vinylon, polyethylene and polyamides.

The fiber reinforced composite material of the present invention isobtained by arranging a plurality of said yarn prepregs or intermediatematerial units, and curing the epoxy resin composition usually byheating.

A prepreg can be molded into a composite material by cutting a prepregsheet, laminating the cut prepreg sheets, and molding them by any ofconventionally widely known methods such as press molding, autoclavemolding and internal pressure molding.

For example, a composite material sheet can be obtained by cutting aprepreg sheet, laminating a predetermined number of the cut prepregsheets in a predetermined fiber axis direction on the surface of a tool,covering them with a bag film, etc., for sealing, degassing the inside,and heating and pressurizing in an autoclave.

A cable-like composite material or a beam-like composite material can beobtained, for example, by arranging a plurality of yarn prepregs,introducing them into a forming die with a desired hole sectional formas practiced with pultrusion, and continuously heating for curing, or asdescribed in said JP-A-6-93579, fixing a plurality of yarn prepregs inthe collected position in the cross section, for arranging to maintainthe reinforcing fibers in all the yarn prepregs parallel to the axialdirection, or covering these yarn prepregs, for example, by braidingwith synthetic fibers such as polyester fibers, to prepare a unitcomposite cable, and continuously heat-curing in an oven.

A fiber reinforced composite material such as twisted cable can beobtained, for example, by twisting uncured unit composite cables, andcontinuously heat-curing in an oven, as described in JP-A-6-93579 andJapanese Patent Publication (Kokoku) No. 686718.

The present invention also provides a concrete member reinforced by afiber reinforced composite material as described above.

In this case, the fiber reinforced composite material can be formedlike, for example, a twisted cable, cable, rod, strip, sheet, etc., butthe form is not limited to these. In particular, a twisted cable issimilar to a so-called steel cable for prestressed concrete in form. So,it can be used like a steel cable for prestressed concrete as a tensionmember of prestressed concrete or a cable for a bridge.

The yarn prepreg of the present invention can be produced by a wetmethod of dissolving a matrix resin into a solvent, to lower itsviscosity, and immersing a continuous fiber bundle for impregnation, ora hot melt method of heating a resin for lowering its viscosity, coatinga roll or release paper with it, to form a film, and pressing acontinuous fiber bundle against it for impregnation.

The yarn prepregs of the present invention can be preferably produced bya hot melt method without using release paper. Specifically, while amolten resin is supplied to the grooves of a rotating grooved roller,fiber bundles are brought into contact with the grooves of the groovedroller at a position downstream in the rotating direction, forimpregnating the fiber bundles with the molten resin. According to thismethod, Wf of the yarn prepregs can be stabilized.

The grooved roller in this case refers to a cylindrical roller which hasgrooves with a certain width and depth formed in the circumferentialdirection. The width of the grooves can be decided to suit the width ofeach yarn prepreg to be obtained, but is preferably 2 mm to 30 mm, morepreferably 3 mm to 20 mm. If the width is less than 2 mm, the width ofthe product obtained is too narrow, and the yarn prepreg obtained is notof sufficient practical use. On the other hand, if the width of thegrooves is more than 30 mm, it becomes difficult to keep the fiberbundles parallel, and the composite material obtained becomes unstablein mechanical properties.

The depth of the grooves can be decided irrespective of the amount ofthe resin to be deposited (hereinafter called Wr) in the yarns to beproduced, but is preferably about 1 mm to 10 mm, more preferably 3 mm to10 mm. If the depth is less than 1 mm, the adjustment of the clearancebetween a blade and groove bottom described later becomes difficult.Even if it exceeds, 10 mm, there is no practical significance, and whenfibers cling during the production of the yarn prepregs, it becomesdifficult to remove the fibers.

The form of the grooves of the grooved roller is not limited to arectangle as described above, and can be a trapezoid, V-shape orU-shape.

When a molten resin is supplied to the grooved roller, it is preferableto supply it to the groove bottoms of the grooved roller, but if theside walls of the grooves are not vertical as in the case of trapezoidor V-shape, the molten resin can also be supplied to the side walls ofthe grooves.

The time during which the fiber bundles are kept in contact with theresin applied on the groove bottoms is decided by the diameter androtating speed of the roller, the contact angle of the fiber bundles,etc. The roller diameter at the groove bottoms is preferably 50 mm to500 mm, more preferably 90 mm to 300 mm in view of easy use. The contactangle between the fiber bundles and the grooved roller is preferably 30to 180°, more preferably 60 to 120°. If the contact angle is less than300, the time of contact between the fiber bundles and the molten resinis so short as to lower resin impregnability, and on the other hand, ifmore than 180°, fibers are likely to cling to the roller. Furthermore,the peripheral speed at the groove bottoms of the roller is preferablyalmost the same as the fiber bundle carrying speed.

According to the present invention, at the groove bottoms where thecontact between the applied resin and the fiber bundles has completed,the resin little remains, and after one revolution of the roller, themolten resin is newly applied to the groove bottoms.

The amount of the resin to be impregnated into the fiber bundles can becontrolled by inserting a blade with a width almost equal to the groovewidth, into each groove of the rotating grooved roller, and adjustingthe clearance formed between the bottom of the groove and the blade.

In this case, the adjusting allowance of the clearance is preferably0.01 mm to 2 mm, more preferably 0.01 mm to 1 mm.

Since a blade is inserted into each groove, it is preferable that itswidth almost agrees with the groove width. If the width of the blade issmaller than the groove width, more than a required amount of the resinis applied through the clearances formed between the side faces of thegroove and the blade to the groove bottom on the downstream side. So, apredetermined Wr cannot be obtained and filament breakage is likely tohappen at both the edges in the width of the yarn prepreg as in the caseof using a flat (groove-less) roller.

The grooved roller is heated to keep the viscosity of the resinpreferably in a range of 1 poise to 200 poises, more preferably in arange of 1 poise to 100 poises.

If the viscosity of the resin is less than 1 poise, the viscosity is toolow, and it becomes difficult to accurately control the amount of theresin applied, simply by adjusting the clearance between the blade andthe groove bottom. If more than 100 poises, the impregnability of theresin into the fiber bundle may become insufficient.

In the present invention, it is more preferable to preheat the fiberbundles, before the fiber bundles come into contact with the moltenresin. The reason is that if the fiber bundles are preheated, theviscosity of the resin declines when the fiber bundles come into contactwith the molten resin, to allow easier impregnation of the resin, and sothat, as compared with a case of no preheating, the fiber bundlecarrying speed can be raised, to improve productivity.

The fiber bundle preheating temperature range is preferably not lowerthan the temperature of the molten resin and not higher than (thetemperature of the molten resin +10° C.). If the preheating temperatureof the fiber bundles is lower than the temperature of the molten resin,the temperature of the resin declines to give a rise in viscosity at themoment when the fiber bundles come into contact with the molten resin,and impregnation may be insufficient. On the other hand, if thepreheating temperature is higher than (the temperature of the moltenresin +100° C.), the resin is gelled, and it becomes difficult to obtaina yarn prepreg of a good grade.

If the fiber bundles are widened before they come into contact with themolten resin, the resin impregnability can be improved. Most preferably,the fiber bundles are preheated while being widened before they comeinto contact with the molten resin.

For spreading the fiber bundles, any known method can be used, forexample, by arranging a plurality of bars alternately in the directionperpendicular to the fiber bundle carrying direction, and stroking thefiber bundles.

In the present invention, it is also possible to impregnate the fiberbundles with the resin by a first grooved roller and then to bring thefiber bundles into contact with at least one rotating heating roller, topromote the impregnation of the resin. In this case, the faces of thefiber bundles to be brought into contact with the second roller can beon the same side as or on the opposite side to the faces brought intocontact with the first grooved roller.

In the present invention, the temperature of the resin impregnated fiberbundles is preferably controlled to be in a range of 0° C. to 35° C.immediately before they are wound around cores. If they are wound atlower than 0° C., the rigidity of the fiber bundles increase, and theyarn prepregs are likely to be folded. On the other hand, if higher than35° C., the resin is likely to migrate in the steps of winding, etc.,and the Wr of the yarn prepregs may be changed.

The yarn prepregs can be controlled in a temperature range of 0° C. to35° C. by circulating cooling water in the roller of the drive stationor applying cooling air to the yarn prepregs, etc.

The present invention also provides a method of winding a yarn prepreg,comprising the steps of impregnating a fiber bundle with a resin, andwinding it at an angle of 2 to 40° around the surface of a core aroundwhich a film made of a material excellent in releasability from the yarnprepreg is formed.

As a core, a paper tube is often used since it is low in cost. However,if a yarn prepreg is directly wound around the surface of a paper tube,the sticky resin of the yarn prepreg is caught by the surface of thepaper tube, to lower the Wr of the unwound yarn prepregdisadvantageously. So, on the surface of a core such as a paper tube, afilm of PVC, polyester, polyamide or polypropylene, etc. is formed, andaround it, the yarn prepreg is wound at an angle of 2 to 40°.

The angle in this case refers to the angle against an axis perpendicularto the axis of the core. If the angle is less than 2°, the yarn prepregis hard to unwind because of the tackiness of the resin. On the otherhand, if the angle is more than 40° C., the yarn prepreg looks untidy,and due to the vibration during transport, etc., the yarn prepreg comesoff from the core. The angle is preferably 5 to 35°.

The present invention also provides a method for producing a tube madeof a fiber reinforced resin, comprising the steps of winding a fiberbundle impregnated with a resin by the above mentioned method, as it is,around a core by the filament winding method; heating the fiber bundletogether with the core, to cure the resin; and removing the core.

The conventional method of producing a tube made of a fiber reinforcedresin by the filament winding method comprises the steps of immersing acontinuous fiber bundle without any resin deposited on it, into a bathcontaining a predetermined resin solution, while winding it around acore; heating it together with the core, to cure the resin; and removingthe core. The present invention is characterized in that a fiber bundleimpregnated with a resin by the above mentioned method, i.e., a yarnprepreg is wound, as it is, around a core by the filament windingmethod. The conventional filament winding method presents problems suchthat Wr is likely to be changed by the winding speed, the concentrationof the resin solution, etc., and that the resin deposited on the fiberbundle excessively must be removed by squeezing. However, in the presentinvention, since Wr is set at a predetermined value in the step of resinimpregnation, a tube made of a fiber reinforced resin stable in fibercontent can be obtained without using the complicated steps of theconventional method.

The present invention also provides a method for producing a tube madeof a fiber reinforced resin, comprising the steps of winding a fiberbundle impregnated with a resin by the above mentioned method, as it is,around a core covered with a flexible tube by the filament windingmethod; removing the core only, to obtain a preform with a flexibletube; installing the preform in a cavity of a mold; and heating whileapplying an internal pressure to the flexible tube, to cure the resin.

The conventional method of producing a tube made of a fiber reinforcedresin as used in a tennis racket comprises the steps of immersing acontinuous fiber bundle without any resin deposited, in a bathcontaining a predetermined resin solution, while winding it around acore covered with a flexible tube by the filament winding method;removing the core only, to obtain a preform with a flexible tube;installing the preform in a cavity of a mold; and heating while applyingan internal pressure to the flexible tube, for curing the resin.

In the present invention, a fiber bundle impregnated with a resin by theabove mentioned method is wound, as it is, around a core covered with aflexible tube by the filament winding method. So, for the same reason asdescribed before, a stable tube made of a fiber reinforced resin can beproduced efficiently without using the conventional steps.

The present invention also provides an apparatus for producing yarnprepregs, comprising a grooved roller for impregnating a fiber bundlewith a molten resin, and a molten resin supplying device for supplyingthe molten resin to the groove bottoms of the grooved roller.

A preferable embodiment of the yarn prepreg producing apparatus of thepresent invention is provided with

a creel for supplying fiber bundles,

a resin melting device,

a molten resin metering and supplying device for supplying the moltenresin to a resin reservoir while metering it,

a molten resin supplying device with the molten resin reservoir, forsupplying the molten resin to a grooved roller,

a grooved roller for impregnating the fiber bundles with the moltenresin, winders for winding the yarn prepregs,

a drive station for carrying the fiber bundles from the creel to thewinders, and

a device for circulating a heating medium to the resin melting device,molten resin metering and supplying device, molten resin supplyingdevice and grooved roller.

That is, continuous fiber bundles are unwound from the creel forsupplying the fiber bundles, and introduced into the grooved roller, tobe impregnated with a molten resin. The grooved roller for impregnatingthe fiber bundles with the molten resin has the resin melting device,molten resin metering and supplying device for supplying the moltenresin to the resin reservoir while metering it, and molten resinreservoir, and the molten resin supplying device for supplying themolten resin to the grooved roller is provided as an attachment.Furthermore, a mechanism capable of supplying a predetermined amount ofthe resin to the continuous fiber bundles is also provided. The fiberbundles are carried from the creel to the winders by the drive station,and finally, the yarn prepregs are wound around cores by the winders.

The apparatus has a device for circulating a heating medium connectedfor heating, to be kept at a predetermined temperature.

The creel for supplying the fiber bundle preferably has a mechanism toallow unwinding at the same unwinding tension even the winding diameterof the fiber bundles changes.

If the resin melting device can bring a heating roller into contact witha solid resin, to melt the resin only at the contact portion, forallowing it to drop in the resin reservoir provided below, this methodis preferably simple in structure. In this method, if a partition platepressed against the heating roller is installed, the resin meltingdevice can also be used as the molten resin metering and supplyingdevice for supplying the molten resin while metering it. That is, if theclearance above the roller surface and the rotating speed and width ofthe roller are changed, the molten resin can be supplied to the resinreservoir, while being metered.

The molten resin metering and supplying device is not limited to theabove method, and any known gear pump type discharger, plunger typedischarger, extruder, microtube pump, etc. can also be used. When a tubepump or gear pump is used as the molten resin metering and supplyingdevice, it is preferably used also as the molten resin supplying devicewith a molten resin reservoir, for supplying the molten resin to thegrooved roller.

The molten resin supplying device with a molten resin reservoir, forsupplying the molten resin to the grooved roller has blades built-in,and is attached to the grooved roller, and the resin collected herepasses through the clearance formed between each blade and each groovebottom, to be applied to the groove bottom.

The grooved roller for impregnating the fiber bundles with the moltenresin is substantially a grooved kiss roller, and the molten resinapplied to the groove bottoms contacts the fiber bundles.

The winders used for winding the yarn prepregs can be known winders.

In view of the object of the present invention, bobbin traverse type ispreferable, but the present invention is not limited to it. For betterappearance of wound package, a winder called edge softening type ispreferred.

The drive station for carrying the fiber bundles from the creel to thewinders is composed of at least one rotating roller, and is preferablyat least 300 mm in its length of contact with the fiber bundles.

The rotating roller is preferably covered with a teflon, silicon rubberor resin, polypropylene resin or film, etc. not to allow the stickyresin of the yarn prepregs to adhere.

The present invention includes a device for circulating a heating mediumto the resin melting device, molten resin metering and supplying device,molten resin supplying device and grooved roller. The device forcirculating a heating medium can be a combination of a hot water deviceand a circulating pump or a combination of an oil heater and acirculating pump.

It is more preferable that a device for preheating the fiber bundles isprovided between the creel for supplying the fiber bundles and thedevice for impregnating the fiber bundles with the molten resin.

The reason is that if the temperature of the fiber bundles is lower thanthe temperature of the molten resin, the resin drops in temperature, torise in viscosity, inhibiting the impregnation of the resin into thefiber bundles at the moment when the fiber bundles come into contactwith the molten resin. The fiber bundle preheating temperature ispreferably not lower than the temperature of the molten resin and nothigher than (the temperature of the molten resin +100° C.) as mentionedbefore.

For preheating the fiber bundles, an ordinary heater such as a hot plateor far infrared heater can be used, but it is most preferable to bringthe fiber bundles into contact with a rotating heating kiss roller,because the generation of fluff can be inhibited and because processingat a high speed is possible. In this case, to inhibit the generation offluff, it is preferable to keep the peripheral speed of the kiss rollerequal to the fiber bundle carrying speed.

The apparatus of the present invention preferably has a device forspreading the fiber bundles between the creel for supplying the fiberbundles and the grooved roller for impregnating the fiber bundles withthe molten resin. The reason is that if the fiber bundles are widened,the resin impregnation can be promoted. In order to allow the fiberbundles to be heated while being widened, if said stroking bars, etc.are arranged in the heating zone, the spreading effect increases.

The grooved roller for impregnating the fiber bundles with the moltenresin in the present invention has a molten resin reservoir, and mayalso contain the molten resin supplying device for supplying the moltenresin into the grooved roller, i.e., a grooved heating roller, blades tobe inside the grooves of the grooved heating roller and a device forcollecting the molten resin. With this construction, the molten resin inthe device for collecting the molten resin passes through the clearanceformed between the tip of each blade and the bottom of each groove ofthe heating roller, to be applied to the groove bottom in apredetermined amount. The amount of the resin to be applied to thegroove bottom is decided by the clearance and the rotating speed of theroller, and if the clearance is constant, a certain Wr can be maintainedirrespective of the fiber bundle carrying speed as far as the peripheralspeed of the groove bottom is the same as the fiber bundle carryingspeed.

In a preferable embodiment of the production apparatus of the presentinvention, the clearance formed between the tip of each blade to beinserted inside each groove of the grooved heating roller and the groovebottom can be controlled in a range of 0.01 mm to 2 mm, more preferably0.01 mm to 1 mm. If the clearance is less than 0.01 mm, the resin cannotbe supplied, hence not deposited, though depending on the viscosity ofthe resin, and if more than 2 mm, the resin is kept flowing, making thecontrol of Wr substantially difficult.

In a preferable embodiment of the production apparatus of the presentinvention, the molten resin supplying device with a molten resinreservoir can be heated, and is located upstream, in the roller rotatingdirection, of the portion where the fiber bundles of the grooved rollerfor impregnating the fiber bundle with the molten resin contact theroller.

With this construction, the molten resin can be efficiently andaccurately applied to the groove bottom surfaces of the grooved rollerin a predetermined amount, and in addition since the region where thefiber bundles contacts the roller is located downstream of this region,the fiber bundles are reliably impregnated with the applied resin, andcarried to the subsequent step.

Furthermore, as described before, a resin metering and supplying devicesuch as a gear pump type discharger, plunger type discharger, extruderor microtube pump, etc. can also be used to supply the resin in apredetermined amount into the grooves of the roller, instead ofcontrolling the supplied amount of the epoxy resin composition byadjusting the clearance between each blade and each groove bottom. Theamount of the resin supplied is preferably at a rate of 1 to 50 g/min.If the supplied amount is smaller than 1 g/min, the resin content in theprepreg may become low. On the contrary, if larger than 50 g/min, theresin content in the prepreg may become high. A more preferable range ofthe amount supplied is 3 to 40 g/min.

Furthermore, the discharger such as a gear pump can be provided for eachgroove of the roller. However, supplying the resin to a plurality ofgrooves on the roller by tournament piping from one discharger ispreferable having regard to operation convenience and cost since thenumber of dischargers can be minimized. One fiber bundle corresponds toeach impregnation groove of the roll, to bring a plurality of carbonfiber bundles into contact with a plurality of grooves.

To control the width (d) of the prepregs, for example, the fiber bundleswith the resin deposited on them are pressed against a grooved roll witha desired groove width, or are stroked by a die with a desired clearanceand as required, pressurized by a roll.

In the method of the present invention, if a carbon fiber bundlesatisfying the following formulae (4) and (5) is used, it is preferablesince a yarn prepreg with a suitable width can be obtained.

F/3,000≦D≦F/1,200  (4)

20,000≦F≦100,000  (5)

EXAMPLES Example 1

Thirty five parts by weight of bisphenol A type epoxy resin “Epikote828” produced by Yuka Shell Epoxy K.K., 30 parts by weight of “Epikote1001”, 35 parts by weight of phenol novolak type epoxy resin “Epikote154” produced by the same manufacturer, 4 parts by weight ofdicyandiamide as a curing agent and 4 parts by weight of3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) as a curing aid werekneaded homogeneously using a kneader, to prepare a matrix resincomposition. The composition was heated at 130° C. for 2 hours, to becured, and the tensile breaking elongation of the cured product was6.3%.

Then, carbon fibers “Torayca” (registered trade name) T700SC-24K-50C(24,000 filaments, 230 GPa in tensile elastic modulus E, 4,900 MPa intensile strength σ, substantially twistless) produced by TorayIndustries, Inc. were opened by spreading bars. Subsequently, said epoxyresin composition controlled at 70° C. was supplied at a rate of 7 g/minto each of the five grooves of a grooved roller heated at 70° C. fromone gear pump type discharger through a piping installed in tournamentstyle, and said carbon fiber bundles were brought into contact with thegrooves of the grooved roller at a position downstream in the rotatingdirection of the roller, to produce yarn prepregs of 30% by weight Wr(70% in Wf). The yarn prepregs obtained were 6.0 mm in width (d).

The density (ρ_(CF)) and unit weight (P_(cf)) of the carbon fibers wererespectively 1.80 and 1.65. The density (ρ_(RESIN)) of the cured resinwas 1.225.

Twenty yarn prepregs obtained as above were collected at a fixed yarncollecting position in a cross section, with the reinforcing fibersarranged in parallel to the axial direction, and they were covered witha knitted fabric of polyester fibers, and cured at 130° C. for 2 hoursin a curing furnace. The volume percent Vf of the carbon fibers in thestrand obtained was 67 vol %. The strand was cut at a length of 800 mm,and woven fabrics of glass fibers of 200 mm in width impregnated with anepoxy resin were wound around the strand at both the ends. It was cured,and attached to Autograph (98 kN in maximum load) produced by ShimadzuCorp., and a tensile test was conducted at a strain speed of 2 mm/min.In this case, the strand was 3.1 GPa in tensile strength and 95% instrength translation rate.

The strands were arranged like a sheet, to produce a prepreg. Eightplies of the prepreg were laminated on the top surface of a flat tool,and covered with a bag film. The pressure inside the bag was reduced,and the laminate was cured at 100° C. for 1 hour and at 130° C. for 1hour (64% in Vf). From this unidirectional composite material, a 25 cmlong specimen was cut out, and subjected to a tensile test according toASTM D 3039-76. The tensile strength was 3.0 GPa and the strengthtranslation rate was 96%.

Furthermore, a 1 cm long specimen was cut out, and subjected to aninterlaminar shear test according to ASTM D 2344, and the interlaminarshear strength was found to be 105 MPa.

The degree of strength translation referred to above is the measuredtensile strength/(the tensile strength of carbon fibers×fiber content byvolume), and the tensile strength of carbon fibers was obtainedaccording to JIS R 7601.

Example 2

Carbon fibers “Torayca” (registered trade name) T700SC-24K-50C (24,000filaments, 230 GPa in E, 4,900 MPa in σ, substantially twistless)produced by Toray Industries, Inc. and the resin composition stated inExample 1 were used to produce yarn prepregs (3.3 mm in width (d)) of30% in Wr by the same method as described in Japanese Patent PublicationNo. 6-93579. Then, a strand (68% in Vf) was obtained as described inExample 1. The strand was 3.1 GPa in tensile strength. Theunidirectional composite material (64% in Vf) was 2.9 GPa in tensilestrength and 93% in the degree of strength translation. The interlaminarshear strength was 101 MPa.

The density (ρ_(CF)) and unit weight (P_(CF)) of the carbon fibers wererespectively 1.80 and 1.65. The density (ρ_(RESIN)) of the cured resinwas 1.225.

Example 3

Yarn prepregs were produced as described in Example 1, except that agrooved roller with 10 mm wide and 5 mm deep grooves was used after hotmelt impregnation with the resin. The yarn prepregs obtained were 9.1 mmin width (d).

The density (ρ_(CF)) and unit weight (P_(cf)) of the carbon fibers wererespectively 1.80 and 1.65. The density (ρ_(RESIN)) of the cured resinwas 1.225.

The strand produced as described in Example 1 was 3.2 GPa in tensilestrength and 96% in degree of strength translation. The unidirectionalcomposite material (63% in Vf) was 2.9 GPa in tensile strength, 95% indegree of strength translation, and 108 MPa in interlaminar shearstrength.

Example 4

Fifty parts by weight of bisphenol A type epoxy resin “Epikote 828”produced by Yuka Shell Epoxy K.K., 30 parts by weight of “Epikote 1001”,20 parts by weight of phenol novolak type epoxy resin “Epikote 154”produced by the same manufacturer, and an epoxy equivalent quantity of4,4′-diaminodiphenylsulfone as a curing agent were kneaded homogeneouslyby a kneader, to produce a matrix resin composition. The composition washeated at 180° C. for 2 hours, to be cured. The tensile breakingelongation of the cured product was 5.2%.

Carbon fibers “Torayca” (“registered trade mark” T700SC-24K-50C (24,000filaments, 230 GPa in E, 4,900 MPa in σ, substantially twistless)produced by Toray Industries, Inc. were opened by spreading bars asdescribed in Example 1. Subsequently, said epoxy resin compositioncontrolled at 70° C. was supplied at a constant rate of 7 g/min to eachof five grooves of a grooved roller heated at 70° C. from one gear pumptype discharger through a piping installed in tournament style, and thecarbon fiber bundles were brought into contact with the grooves of thegrooved roller at a position downstream in the rotating direction of theroller, to produce yarn prepregs of 30% by weight Wr (70% in Wf). Theyarn prepregs obtained were 6.2 mm in width (d).

The density (ρ_(CF)) and unit weight (P_(cf)) of the carbon fibers wererespectively 1.80 and 1.65. The density (ρ_(RESIN)) of the cured resinwas 1.280.

A strand of 66% in Vf was obtained by curing under the same conditionsas in Example 1 except that 20 yarn prepregs were cured at 180° C. Thestrand was 3.0 GPa in tensile strength and 93% in degree of strengthtranslation. The unidirectional composite material (64% in Vf) was 3.1GPa in tensile strength, 96% in degree of strength translation and 98MPa in interlaminar shear strength.

Comparative Example 1

Yarn prepregs (70% in Wf and 30% in Wr) were produced as described inExample 1, except that the grooved roller was not used. The yarnprepregs obtained were 12.0 mm in width (d).

A strand was produced as described in Example 1, but when yarn prepregswere collected, the individual yarn prepregs were distorted. The strandobtained was as poor as 2.5 GPa in tensile strength and 75% in degree ofstrength translation. A prepreg sheet was produced by the drum windingmethod as described in Example 1, but the yarns were distorted at theguide portion, and the unidirectional composite material obtained was aspoor as 2.6 GPa in tensile strength and 82% in degree of strengthtranslation.

Comparative Example 2

Yarn prepregs were produced (70% in Wf and 30% in Wr) as described inExample 1 except that a grooved roller with 2 mm wide and 5 mm deepgrooves was used after resin impregnation. The yarn prepregs obtainedwere 2.1 mm in width (d).

A strand was produced as described in Example 1, and it was as good as3.2 GPa in tensile strength and 95% in degree of strength translation.On the other hand, a prepreg sheet was produced by the drum windingmethod as described in Example 1. The unidirectional composite materialobtained was 2.4 GPa in tensile strength, 76% in degree of strengthtranslation and 60 MPa in interlaminar shear strength.

Example 5

(1) Preparation of matrix resin composition

The following raw materials were kneaded using a kneader, to produce amatrix resin composition.

Bisphenol A type epoxy resin (Epikote 8282 produced by Yuka Shell EpoxyK.K.) 35 parts by weight

Bisphenol A type epoxy resin (Epikote 1001 produced by Yuka Shell EpoxyK.K.) 30 parts by weight

Phenol novolak type epoxy resin (Epikote 154 produced by Yuka ShellEpoxy K.K.) 35 parts by weight

Fine rubber particles (0.2 μm in average particle size) (ParaloidEXL2655 produced by Kureha Chemical Industry Co., Ltd.) 10 parts byweight

Dicyandiamide 4 parts by weight

DCMU 4 parts by weight

This epoxy resin composition was 269 in epoxy equivalent weight. Thecured resin product was 6.5% in tensile breaking elongation. The resinwas 1.94 MN/m^(3/2) in K_(1C).

(2) Preparation of prepreg

Carbon fibers “Torayca” (registered trade name) T700SC-24000-50C (230GPa in E, 4900 MPa in σ, and 7200 deniers in fineness) produced by TorayIndustries, Inc. arranged in one direction were impregnated with saidresin composition, but heat melted, to achieve a resin content of 30% byweight, and a prepreg sheet was produced by the drum winding method.

(3) Preparation of composite material

Eight plies of the prepreg sheet were laminated on the top surface of aflat tool, and covered with a bag film, and the inside pressure wasreduced. The laminate was cured at 100° C. for 1 hour and at 135° C. for1 hour in an oven. The Tg of the cured product was measured at a heatingrate of 10° C./min by differential thermal analysis and found to be 130°C.

From the unidirectional composite material, a 25 cm long specimen wascut out, and subjected to a tensile test according to ASTM D 3039-76.The tensile strength was 2.85 GPa and the degree of strength translationwas 97%.

The degree of strength translation referred to here is the measuredtensile strength/(the tensile strength of reinforcing fibers×fibercontent by volume), and the tensile strength of reinforcing fibers wasobtained according to JIS R 7601.

Example 6

The following raw materials were kneaded using a kneader, to produce amatrix resin composition.

Bisphenol A type epoxy resin (Epikote 828 produced by Yuka Shell EpoxyK.K.) 25 parts by weight

Bisphenol A type epoxy resin (Epikote 1001 produced by Yuka Shell EpoxyK.K.) 35 parts by weight

Phenol novolak type epoxy resin (Epikote 154 produced by Yuka ShellEpoxy K.K.) 35 parts by weight

Cyclohexanedimethanol diglycidyl ether (Heloxy MK107 produced by RhonePoulenc) 5 parts by weight

Fine rubber particles (0.2 μm in average particle size) (ParaloidEXL2655 produced by Kureha Chemical Industry Co., Ltd.) 7 parts byweight

Dicyandiamide 4 parts by weight

DCMU 4 parts by weight

The epoxy resin composition was 281 in epoxy equivalent weight. Thecured resin product was 6.2% in tensile breaking elongation. The resinwas 2.03 MN/m^(3/2) in fracture toughness K_(1C).

The same carbon fibers as used in Example 5 were used, to produce aprepreg sheet and a unidirectional composite material as described inExample 5. A tensile test was conducted also as described in Example 5.The tensile strength was 2.88 GPa and the degree of strength translationwas 98%.

Example 7

Evaluation was carried out as described in Examples 5 and 6, except thatthe following matrix resin composition was produced.

Bisphenol A type epoxy resin (Epikote 828 produced by Yuka Shell EpoxyK.K.) 35 parts by weight

Bisphenol A type epoxy resin (Epikote 1001 produced by Yuka Shell EpoxyK.K.) 25 parts by weight

Phenol novolak type epoxy resin (Epikote 154 produced by Yuka ShellEpoxy K.K.) 28 parts by weight

Resorcinol glycidyl ether (Denacol EX201 produced by Nagase Kasei K.K.)12 parts by weight

Fine rubber particles (0.2 μm in average particle size) (ParaloidEXL2655 produced by Kureha Chemical Industry Co., Ltd.) 7 parts byweight

Dicyandiamide 4 parts by weight

DCMU 4 parts by weight

The epoxy resin composition was 247 in epoxy equivalent weight. Thecured resin product was 6.8% in tensile breaking elongation. The resinwas 2.11 MN/m^(3/2) in fracture toughness K_(1C).

In this case, the unidirectional composite material was 2.82 GPa intensile strength and 96% in degree of strength translation.

Example 8

Evaluation was carried out as described in Example 5, except that thefollowing raw materials were kneaded using a kneader, to produce amatrix resin composition.

Bisphenol A type epoxy resin (Epikote 828 produced by Yuka Shell EpoxyK.K.) 35 parts by weight

Bisphenol A type epoxy resin (Epikote 1001 produced by Yuka Shell EpoxyK.K.) 25 parts by weight

Phenol novolak type epoxy resin (Epikote 154 produced by Yuka ShellEpoxy K.K.) 28 parts by weight

Resorcinol glycidyl ether (Denacol EX201 produced by Nagase Kasei K.K.)12 parts by weight

Fine rubber particles (0.2 μm in average particle size) (ParaloidEXL2655 produced by Rohm & Haas) 15 parts by weight

Dicyandiamide 4 parts by weight

DCMU 4 parts by weight

The epoxy resin composition was 247 in epoxy equivalent weight. Thecured resin product was 7.0% in tensile breaking elongation. The resinwas 2.34 MN/m^(3/2) in fracture toughness K_(1C).

The unidirectional composite material was 2.91 GPa in tensile strengthand 99% in degree of strength translation.

Example 9

Evaluation was carried out as described in Example 5, except that thefollowing raw materials were kneaded using a kneader, to produce amatrix resin composition.

Bisphenol A type epoxy resin (Epikote 828 produced by Yuka Shell EpoxyK.K.) 35 parts by weight

Bisphenol A type epoxy resin (Epikote 1001 produced by Yuka Shell EpoxyK.K.) 25 parts by weight

Phenol novolak type epoxy resin (Epikote 154 produced by Yuka ShellEpoxy K.K.) 28 parts by weight Resorcinol glycidyl ether (Denacol EX201produced by Nagase Kasei K. K.) 12 parts by weight

Fine rubber particles (0.07 μm in average particle size) (XER-91produced by Japan Synthetic Rubber Co., Ltd.) 15 parts by weight

Dicyandiamide 4 parts by weight

DCMU 4 parts by weight

The epoxy resin composition was 247 in epoxy equivalent weight. Thecured resin product was 6.5% in tensile breaking elongation. The resinwas 1.84 MN/m^(3/2) in fracture toughness K_(1C).

The unidirectional composite material was 2.73 GPa in tensile strengthand 93% in degree of strength translation.

Example 10

(1) Preparation of matrix resin composition

The following raw materials were kneaded using a kneader, to produce amatrix resin composition.

Bisphenol A type epoxy resin (Epikote 828 produced by Yuka Shell EpoxyK.K.) 25 parts by weight

Bisphenol A type epoxy resin (Epikote 1001 produced by Yuka Shell EpoxyK.K.) 35 parts by weight

Phenol novolak type epoxy resin (Epikote 154 produced by Yuka ShellEpoxy K.K.) 35 parts by weight

Cyclohexanedimethanol diglycidyl ether (Heloxy MK107 produced by RhonePoulenc) 5 parts by weight

Fine rubber particles (0.2 μm in average particle size) (ParaloidEXL2655 produced by Kureha Chemical Industry Co., Ltd.) 7 parts byweight

Dicyandiamide 4 parts by weight

DCMU 4 parts by weight

The epoxy resin composition was 281 in epoxy equivalent weight. Thecured resin product was 6.2% in tensile breaking elongation. The resinwas 2.03 MN/m^(3/2) in fracture toughness K_(1C).

The unidirectional composite material was 2.79 GPa in tensile strengthand 95% in degree of strength translation.

Example 11

The following raw materials were kneaded using a kneader, to produce amatrix resin composition.

Bisphenol A type epoxy resin (Epikote 828 produced by Yuka Shell EpoxyK.K.) 21 parts by weight

Bisphenol A type epoxy resin (Epikote 1001 produced by Yuka Shell EpoxyK.K.) 38 parts by weight

Phenol novolak type epoxy resin (Epikote 154 produced by Yuka ShellEpoxy K.K.) 35 parts by weight

Cyclohexanedimethanol diglycidyl ether (Heloxy MK107 produced by RhonePoulenc) 6 parts by weight

Fine rubber particles (0.2 μm in average particle size) (ParaloidEXL2655 produced by Kureha Chemical Industry Co., Ltd.) 7 parts byweight

Dicyandiamide 3.5 parts by weight

DCMU 4 parts by weight

The epoxy resin composition was 289 in epoxy equivalent weight. Thecured resin product was 6.2% in tensile breaking elongation. The resinwas 2.13 MN/m^(3/2) in fracture toughness K_(1C).

Carbon fibers “Torayca” T700SC-1200-50C (230 GPa in E, 4900 MPa in σ,7200 deniers in fineness) produced by Toray Industries, Inc. wereimpregnated with the above resin composition, but heat melted, toachieve a resin content of 30% by weight, while being wound around papertubes as they are, to produce 4 mm wide yarn prepregs.

Then, twenty yarn prepregs were bundled, with their fiber axesmaintained in parallel, introduced into a die heated to 130° C., anddrawn to continuously cure the matrix resin, for obtaining a linearcomposite material of 3.6 mm in diameter. The composite material was cutat a length of 800 mm, and 200 mm wide woven fabrics of glass fibersimpregnated with an epoxy resin were wound around the composite materialat both the ends, and cured. The specimen was installed in Autograph (98kN in maximum load) produced by Shimadzu Corp., and a tension test wasconducted at a strain speed of 2 mm/min.

In this case, the linear composite material was 2.82 GPa in tensilestrength and 96% in degree of strength translation.

Example 12

Carbon fibers “Torayca” T700SC-12000-50C (230 GPa in E, 4900 MPa in σ,7200 deniers in fineness) produced by Toray Industries, Inc. and theresin composition described in Example 11 were used to produce a unitcomposite cable to achieve a resin weight content of 34 vol % accordingto the method stated in JP-A-6-93579, and the tensile strength wasmeasured as described in Example 5.

In this case, the linear composite material was 3.04 GPa in tensilestrength and 94% in degree of strength translation.

Example 13

Eleven yarn prepregs described in Example 11 were collected, with theirfiber axes maintained in parallel, and covered around them withsynthetic fibers by braiding, to obtain an uncured strand. Seven suchstrands were twisted, while being continuously heated and cured in acuring furnace at 130° C., to produce a twisted composite material cableof about 13 mm in diameter. The twisted composite material cable was cutat a length of 1000 mm, and was fixed at both the ends for 300 mm byexpansive mortar. The specimen was installed in a tensile tester (500 kNin maximum load) produced by Instron, and a tension test was conductedat a strain speed of 1 mm/min. In this case, the twisted compositematerial cable was 280 kN in tensile breaking yield.

Example 14

Three twisted composite material cables described in Example 13 astension members, two reinforcing bars D13, reinforcing bars D10 asstirrups and ready mixed concrete were used to manufacture a 4.4 m longbeam with a T section of 40 cm in height, 40 cm in width and 15 cm inweb width. It was manufactured outdoors, using a wooden mold. Theconcrete was water spray-cured for 3 days, and at age of 11 days, themold was dismantled. Then, it was air-cured.

The strain introduced into the twisted composite material cable was 70%of the breaking yield, and the beam was designed to be broken at thetwisted composite material cable.

The concrete beam as a simple beam with a span of 4.0 m was loaded attwo points with a pure bending section of 0.8 m, and controlled to bedisplaced in one direction gradually increasingly. After a bending crackoccurred, the beam was once unloaded, and subsequently displaced untilbreaking occurred.

The load was measured by a load cell, and the displacement was measuredby a high sensitivity type displacement seismograph. The strain of thetension member was measured by a wire strain gauge.

The bending ultimate yield of the beam member was 232 kN which wellagreed with an analytical value of 227 kN, and confirmed that they canbe calculated and designed like those of a beam using a conventionalsteel wire for prestressed concrete.

Comparative Example 3

Evaluation was carried out as described in Example 5, except that thefollowing raw materials were kneaded using a kneader, to produce amatrix resin composition.

Bisphenol A type epoxy resin (Epikote 828 produced by Yuka Shell EpoxyK.K.) 35 parts by weight

Bisphenol A type epoxy resin (Epikote 1001 produced by Yuka Shell EpoxyK.K.) 30 parts by weight

Phenol novolak type epoxy resin (Epikote 154 produced by Yuka ShellEpoxy K.K.) 35 parts by weight

Dicyandiamide 4 parts by weight

DCMU 4 parts by weight

The epoxy resin composition was 269 in epoxy equivalent weight. Thecured resin product was 5.5% in tensile breaking elongation. The resinwas 1.06 MN/m^(3/2) in fracture toughness K_(1C).

The unidirectional composite material was 2.50 GPa in tensile strengthand 85% in degree of strength translation.

Comparative Example 4

Evaluation was carried out as described in Example 5, except that thefollowing raw materials were kneaded using a kneader, to produce amatrix resin composition.

Bisphenol A type epoxy resin (Epikote 828 produced by Yuka Shell EpoxyK.K.) 15 parts by weight

Metaaminophenol type epoxy resin (ELM120 produced by Sumitomo ChemicalCo., Ltd.) 50 parts by weight

Phenol novolak type epoxy resin (Epikote 154 produced by Yuka ShellEpoxy K.K.) 35 parts by weight

Fine rubber particles (0.2 μm in average particle size) (ParaloidEXL2655 produced by Kureha Chemical Industry Co., Ltd.) 7 parts byweight

Dicyandiamide 4 parts by weight

DCMU 4 parts by weight

The epoxy resin composition was 149 in epoxy equivalent weight. Thecured resin product was 3.8% in tensile breaking elongation. The resinwas 1.25 MN/m^(3/2) in fracture toughness K_(1C).

The unidirectional composite material was 2.56 GPa in tensile strengthand 87% in degree of strength translation.

Comparative Example 5

(1) Preparation of matrix resin composition

Evaluation was carried out as described in Example 5, except that thefollowing raw materials were kneaded using a kneader, to produce amatrix resin composition.

Bisphenol A type epoxy resin (Epikote 828 produced by Yuka Shell EpoxyK.K.) 25 parts by weight

Bisphenol A type epoxy resin (Epikote 1001 produced by Yuka Shell EpoxyK.K.) 35 parts by weight

Phenol novolak type epoxy resin (Epikote 154 produced by Yuka ShellEpoxy K.K.) 35 parts by weight

Cyclohexanedimethanol diglycidyl ether (Heloxy MK107 produced by RhonePoulenc) 5 parts by weight

CTBN.epoxy reaction product 10 parts by weight

Dicyandiamide 4 parts by weight

DCMU 4 parts by weight

The CTBN.epoxy reaction product was the reaction product (9600 in numberaverage molecular weight) of liquid rubber Hycar CTBN1300x13 (27% in ANcontent, produced by Ube Industries, Ltd.) and Epikote 828. The epoxyresin composition was 288 in epoxy equivalent weight. The cured resinproduct was 5.8% in tensile breaking elongation. The resin was 1.35MN/m^(3/2) in fracture toughness K_(1C).

The unidirectional composite material was 2.41 GPa in tensile strengthand 82% in degree of strength translation.

Example 15

FIG. 1 is a schematic drawing showing an example of the apparatus forproducing yarn prepregs of the present invention.

FIG. 2 is a schematic plan view showing a grooved roller. FIG. 3 is aschematic vertical view showing the grooved roller.

As shown in FIG. 1, continuous fiber bundles 2 wound around a creel 1are unwound to be brought into contact with the bottom of a groovedroller 3, and are guided through a drive station 8 to winders, to bewound. Close to the grooved roller 3, a molten resin supplying device 4with bladed 5A at the tip, provided with a bottom plate for storing theresin is installed, and a resin supplying device 7 is installed abovethe molten resin supplying device 4. The resin supplying device 7 has aheating roller 7A, and a resin block 7B supplied to the heating roller7A is rendered molten by the heating roller 7A. The molten resin ispressed against the heating roller 7A by a partition plate 7C. With thisconstruction, the molten resin is metered and supplied to a resinreservoir 4.

The grooved roller 3 has grooves 10 as shown in FIGS. 2 and 3. Betweenthe bottoms of the grooves 10 and the blades 5A, certain clearances 6are formed, and by the rotation of the grooved roller 3, the resin inthe resin reservoir is applied to the groove bottoms in a predeterminedamount respectively, so that the fiber bundles 2 running in contact withthe grooves 10 may be impregnated with the resin.

In the above apparatus, carbon fibers Torayca T700SC-24000-50C and anepoxy resin composition were used to produce yarn prepregs.

The epoxy resin composition consisted of 20 parts of epi-bis liquidresin Epikote 828, 45 parts of epi-bis solid resin Epikote 1001, 35parts of phenol novolak type epoxy resin Epikote 154, 35 parts ofdicyandiamide as a curing agent and 4 parts of DCMU(3,4-dichlorophenyl-1,1-dimethylurea).

The temperature of the grooved kiss roller and the temperature of theresin reservoir were kept at 80° C., and the epoxy resin compositionmelted at 80° C. was supplied in a certain amount to the portion. Inthis case, the clearance between each blade and each groove bottom waschanged in a range of 0.12 mm to 0.18 mm, and the yarn carrying speedwas changed between 5 m/min and 30 m/min, to produce yarn prepregs.Later, a solvent (methyl ethyl ketone) was used to remove the epoxyresin composition, and Wr was measured. The groove width was 10 mm, andthe resin viscosity was 45 poises (80° C.). The results are shown inTable 1.

As shown in Table 1, according to the present invention, irrespective ofthe fiber bundle carrying speed, Wr was kept constant, and solvent-lessyarn prepregs with a predetermined Wr can be efficiently produced byadjusting the clearance only.

Example 16

Yarn prepregs were produced as described in Example 15, except that theangle was changed between 1 to 45° C., and the prepreg wound as bobbins.The yarn prepreg bobbins were unwound in a room at 23° C. at a yarnspeed of 3 m/min, to measure the unwinding tension, for evaluation ofunwindability. The results are shown in Table 2. It can be seen thatyarn prepregs can be unwound without any problem at a low tension in anangle range of 2 to 40°.

Example 17

While yarn prepregs were produced as described in Example 15, they werewound at an angle of about 30° around mandrels covered with a 50 μmthick nylon tube, directly mounted on a filament winding device, insteadof bobbins, and the mandrels were removed. Each wound preform was placedin a mold with a cavity with a form of a racket frame, and while air wasblown into the nylon tube, the mold was heated at 130° C. for 30minutes, to cure the epoxy resin composition, thus obtaining a compositematerial with a form of a racket frame. A good racket frame free fromvoids and without any problem in appearance and frame rigidity could beobtained.

Industrial Applicability

The epoxy resin composition, yarn prepreg and intermediate material ofthe present invention can provide a fiber reinforced composite materialand a concrete member which can be widely used in general industrialfields such as aerospace, sports, and civil engineering andarchitecture.

TABLE 1 Clearance (mm) Carrying speed (m/min) Wr 0.12  5 0.17 10 0.17 200.17 30 0.17 50 0.16 0.15  5 0.29 10 0.30 20 0.30 30 0.29 50 0.30 0.18 5 0.40 10 0.40 20 0.40 30 0.40 50 0.39

TABLE 2 Angle Unwinding tension (°) (g) Evaluation result  1 1500 Unwinding not allowed halfway  2 850 Yarns disordered a little 10 700Unwinding could be achieved without any problem 40 680 Unwinding couldbe achieved without any problem 45 650 Deformation occurred duringunwinding

What is claimed is:
 1. A yarn prepreg comprising a reinforcing fiber bundle and an epoxy resin, wherein the content by weight of the fiber bundle (%), Wf, the number of filaments in the fiber bundle, F, and the width of the prepreg (mm), d, satisfy the following formulae (1) to (3): 50≦Wf≦80  (1) 20,000≦F≦100,000  (2) F/8,000≦d≦F/2,400   (3).
 2. The yarn prepreg according to claim 1, wherein the reinforcing fiber bundle is selected from the group consisting of carbon fibers, silicon carbide fibers, glass fibers and aramid fibers.
 3. The yarn prepreg according to claim 2, wherein the reinforcing carbon fiber bundle is a substantially twistless continuous carbon fiber bundle of 1.3 to 8.0 g/m in weight.
 4. The yarn prepreg according to claim 2, wherein the reinforcing carbon fiber bundle is continuous carbon fibers of 200 Gpa or more in tensile elastic modulus and 38,000 kJ/m³ or more in fracture strain energy.
 5. The yarn prepreg according to claim 1, wherein the epoxy resin contains dicyandiamide as a curing agent, and the tensile breaking elongation of the resin obtained by heat-curing the epoxy resin at 130° C. for 2 hours is 5% or more.
 6. The yarn prepreg according to claim 1, wherein the epoxy resin contains diaminodiphenylsulfone as a curing agent, and the tensile breaking elongation of the resin obtained by heat-curing the epoxy resin at 180° C. for 2 hours is 5% or more.
 7. The yarn prepreg according to claim 1, wherein the interlaminar shear strength of its cured composite material is 65 to 140 MPa.
 8. A yarn prepreg according to claim 1 or 2, wherein the epoxy resin is an epoxy resin composition comprising: an epoxy resin mixture comprising two or more epoxy resins in such a manner that 100 weight parts of the epoxy resin mixture contains 40 to 79 parts of a monofunctional or bifunctional epoxy resin and 21 to 60 parts of a trifunctional or higher functional epoxy resin, the epoxy equivalent weight of the epoxy resin mixture being 210 to 370; fine particles comprising a rubber ingredient, the fine particles being insoluble in the epoxy resins; and a curing agent.
 9. The yarn prepreg according to claim 8, wherein the reinforcing carbon fiber bundle is a substantially twistless continuous carbon fiber bundle of 1.3 to 8.0 g/m in weight.
 10. The yarn prepreg according to claim 9, wherein the reinforcing carbon fiber bundle is continuous carbon fibers having tensile elastic modulus of 200 GPa or more and fracture strain energy of 38,000 kJ/m³ or more.
 11. An intermediate material for a fiber reinforced composite material, wherein a plurality of the yarn prepregs of claim 1 is arranged with their fiber axes kept in parallel.
 12. The intermediate material for a fiber reinforced composite material according to claim 11, wherein synthetic fibers are wound around said intermediate material.
 13. A fiber reinforced composite material, obtained by curing the yarn prepreg of claim
 8. 14. A fiber reinforced composite material, wherein the intermediate material of claim 12 is twisted together and cured.
 15. A concrete member, reinforced by the fiber reinforced composite material of claim 13 or
 14. 16. The yarn prepreg according to claim 1, wherein the yarn prepreg satisfies the following formula: F/7,000≦d≦F/2,700.
 17. The yarn prepreg according to claim 1, wherein the yarn prepreg satisfies the following formula: F/6,000≦d≦F/3,000. 